Early elevated levels of soluble triggering receptor expressed on myeloid cells-1 in subarachnoid hemorrhage patients

Early brain injury (EBI) contributes to poor prognosis of subarachnoid hemorrhage (SAH). This study aimed to clarify whether triggering receptor expressed on myeloid cells-1 (TREM-1) was implicated in the inflammatory mechanisms of EBI. The cerebrospinal fluid (CSF) levels of soluble TREM-1 (sTREM-1), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) as well as plasma levels of white blood cells (WBC) count and C-reactive protein in 17 SAH patients at early stage (within the EBI period) and 9 volunteers were observed. Also World Federation of Neurosurgical Societies (WFNS) scale of SAH patients was calculated on admission. Compared to controls, increased CSF levels of sTREM-1 (t = 5.66, P < 0.001), TNF-α (t = 5.41, P < 0.001) and IL-6 (t = 2.98, P = 0.007) as well as elevated plasma WBC counts (t = 7.61, P < 0.001) and C-reactive protein levels (t = 3.91, P = 0.001) were found in SAH patients. Considering the increased WBC counts in SAH group, covariate analysis was also performed when comparing patients’ sTREM-1 levels with respect to controls and no obvious difference was found (F = 0.982, P = 0.332). For SAH group, early CSF concentrations of sTREM-1 were correlated with those of both TNF-α (r = 0.582, P = 0.014) and IL-6 (r = 0.593, P = 0.012). Also the CSF sTREM-1 levels were positively correlated with WBC counts (r = 0.629, P = 0.007) and C-reactive protein levels (r = 0.804, P < 0.001) as well as WFNS scale (r = 0.835, P < 0.001). This study showed an early increased sTREM-1 CSF level in SAH patients, which correlated with inflammation intensity post-SAH and clinical severity, indicating that TREM-1 may participate in the inflammatory mechanisms of EBI.